If a page is using pretty permalinks, then the request is always at /index.php. The file used to generate the page is going to be in your theme directory (e.g. /wp-content/themes/twentyten). I reworded your question to reflect this.
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John P BlochMar 24 '11 at 16:55

I may be misunderstanding your question, but in WordPress that page is not related directly to a php file. If you are looking in the WordPress backend, you can go to either Posts or Pages and find that title, then hover over it and look in the status bar for the Post/Page ID, if that's what you're trying to find. Sorry not to be more help - maybe you can explain what you're looking for in a different way?